1. Field of the Invention
The present invention is a sucker rod pump that employs double standing valves and does not have a traveling valve. Specifically the present pump is particularly suited for use in gas producing coal bed wells to pump off excess water from the well so that gas can be produced, although the pump is not limited to this use.
2. Description of the Related Art
Gas producing coal bed wells also produce water. This water must be removed from the wells so that the wells can continue to produce gas. Prior art pumps that are employed to remove this water from the wells utilize a combination of a standing valve and a traveling valve. The standing valve attaches to the tubing via a hold down device provided on the pump that engages a seating shoe on the tubing. Thus the standing valve remains stationary at the bottom of the well while in service. The traveling valve is attached to the rod string and moves in a reciprocating manner at the bottom of the well in conjunction with the up and down movement of the rod string. The water in the coal bed wells contains fine particles of coal that tend to clog the valves of these prior art pumps.
The present invention addresses this problem by providing a pump that has two standing valves and no traveling valve. The two standing valves are less likely to be fouled by fine particles of coal than the prior art pumps employing a combination of a traveling valve and a standing valve.
Another shortcoming of prior art sucker rod pumps is that they tend to gas lock. This is due in large part to the fact that, as the travelling valve moves upward in the well, the traveling valve moves a considerable distance away from the standing valve, creating a large fluid chamber between the two valves where gas can accumulate and cause the pump to gas lock. The present invention addresses this problem by maintaining its two standing valves in close proximity to each other and having the chamber where fluid accumulates located above both of the two standing valves.
Further, prior art sucker rod pumps function by pulling or lifting the fluid from the bottom of the well in association with the upstroke of the rod string. This means that the motor that moves the rod up and down in the well must work hard to lift the weight of both the rod string and the fluid column that is being pumped to the surface.
The present invention addresses this shortcoming by using the weight of the rod string to push the fluid to the top in association with the down stroke of the rod. When the rod string is lifted with the present invention, the motor that moves the rod up and down in the well only lifts the weight of the rod string, and not the weight of the fluid column that is being pumped to the surface. By using the weight of the rod string to push the fluid to the surface of the well, this creates less strain on the motor. Also because the motor is not working as hard, less energy is needed to pump the fluid to the top of the well, resulting in energy savings.
The present invention is a specialized pump for the coal bed gas fields that helps pump the fluid off the well to let the gas flow. Most of these wells will produce coal dust that will pack and bind up a conventional pump. The design of this pump will keep the piston from sticking. As the piston is a solid rod and pushes the fluid to the surface, there is much less work for the unit to do since it uses the weight of the rod string to push the fluid, rather than lifting the fluid with the rod string. The motor only uses power to lift the rod string. On the upstroke, the housing fills with fluid and on the down stroke, the fluid is pushed out a bottom discharging valve, keeping the seating assembly from sanding in. The barrel of this pump has a beveled wiping edge on its upper end to keep the piston rod free from coal dust as it strokes. The barrel is short and the length of the stroke is adjusted with the length of the housing. With the shorter barrel, there is less area inside to bind. This makes it less expensive to repair. The wearing parts inside the barrel are smaller, thereby saving on the cost of spare parts. This pump will provide greater savings on downtime and repair than a common down hole pump. This cost savings will offset the slightly higher initial cost of this pump. The pump can be installed with any conventional hold down assembly. With improved materials such as carbide or ceramic valves and nickel carbide barrel, the pump will provide for long and profitable runs on wells.